Improvement in duplex telegraphs



T Ems-0N; Duplex Telegraphs.

I Patented Sept. 3, 1878.

, p MM yo, O KW UNITED STATES PATENT OFFICE.

THOMAS A. EDISON, OF NE\VARK, NEW JERSEY, ASSIGNOR OF ONE-HALF HIS RIGHT TO GEORGE B. PRESCOTT, OF NEW YORK CITY.

IMPROVEMENT lN DUPLEX TELEGRAPHS.

Specification forming part of Letters Patent No. 207,723, dated September 3, 1878 application filed September 1, 1874.

To all whom it may concern:

Be it known that I, THOMAS A. EDISON, of Newark, in the State of New Jersey, have invented an Improvement in Duplex Telegraphs, of which the following is a specification:

Where two persons are sending and two receiving, one at each end, the entire line is sometimes deranged by a signal from one of the receivers to repeat. My invention is made to allow either party that is receiving to interrupt the person sending to him, so that he is thereby warned to repeat, and that without interfering with the other message that is being sent or received.

In the diagram drawing, a is the line; b, the receiving relay-instrument. (Z is a helix around the same core as b; and this helix is in a circuit passing to the artificial line and rheostat e, and this rheostat is to be adjusted to equal the line, so that the pulsation from the sending-station, acting in reverse in the helices b and (1, produces no magnetizing effect in the core, but the pulsation from the distant station, passing along 0, acts in b, unbalanced, and either produces the sound by the armature-magnet or else works a local circuit and sounder. The pulsation received from the distant station passes by 3, f, and 4 to the earth-connection.

The lever f is operated to give the pulsations that are sent upon the line, and these pulsations divide at 5, passing equally through the helices g and h, thence through the helices b and d aforesaid.

The helices g and h are of a differential polarized relay, the tongue or polarized armaturelever 71 of which forms a circuit-breaker in the local circuit k l m, and in this circuit the key I acts to open or close the circuit, and, by the electro-magnet m, operate the lever f and send the pulsations upon the line.

The main battery 0 is connected by wires 10 11 to closing-points 12 13, and the reversin g-lever 1' has springs 14 15 and an insulated arm, 8. *vvhenthe key I is operated the lever fcloses 1s and 1c, asdwithth lever in the position shown the circuit is closed by 10 12 s 15 to the ground, there dividing, par ing through c d h to 3, part going to dis "S statlon, thence by a b g to 3, whence the unite currents pass by 3, 18, 19, 20, 14,1", 13, and 11 to the battery. By these connections the pulsations are sent to the distant station and received there in a similar instrument. It will be apparent that at the sending-station the current divides at 5, and, passing through both 9 and h, the polarized armature will be retained in the normal position, with the circuit of 70 Z m closed, regardless of whether the current sent is reversed or not but the current from the distant station only acts in 9; hence the polarized tongue is changed by the reversal of the battery-connection at the distant station, so that if the receiver closes the key 22 he does not interfere with the party sending by the key I from his own station, but, the batteryconnection being reversed, the diflerent-ial relay at the distant station is changed by the change of polarity in g, and the party sending the message is warned to repeat by the fact that his own magnet m does not work, because the polarized tongue has broken the circuit of the magnet m, and it will not respond to his key I. It is to be remarked that the receiving-operator only closes his key '11 sufficiently long to give the signal, and then releases it, so that the parts resum e their normal condition to allow of the message being again sent to him. The reversal of the polarity at the sending-station does not change the balanced condition of 1) cl, nor make any difference in the action at the distant station, because that current sent is operative in b at the receiving-station, whether of one polarity or the other.

I do not herein claim the construction or arrangement of the reversing lever or key 1', except in combination with other portions of the apparatus, as hereinafter specified, as the same is fully described in another application I claim as my invention The differential polarized relay-magnet g h and local circuit containing the key I, armature-lever 17, and. magnet m, in combination with the reversing-key r and circuit-connections, substantially as set forth.

Signed by me this 19th day of August, A.

THOS. A. EDISON.

Witnesses CHAS. H. SMITH, Gno. T. PINCKNEY.

of even date herewith, and designated as (Jase 

